Process for oxidation of secondary esters of phosphorous acid to primary and secondary esters of phosphoric acid



substituted alkyl, halo-substituted United States Patent This invention relates to the preparation of esters of phosphoric acid. More particularly, it relates to the oxidation of secondary esters of phosphorous acid in the presence of a catalyst to form the corresponding primary and secondary esters of phosphoric acid.

Secondary esters of phosphorous acid have the general formula wherein R maybe aliphatic or aromatic. It is known in the art thatsecondary esters of phosphorous acid (secondary phosphites) are not amenable to oxidation. Kosolapolf, on page 194 of the text, Organo Phosphorus Compounds, published by Wiley and Sons (1958), states .that the secondary esters of phosphorous acid exist substantially in'the ketone form. To support the pentavalent .ketone formula of these esters, illustrated in Formula 1,

their lack.of oxidizability, true acidic characteristics, inability to add cuprous halides, and other physical properties are cited. Thus, this structure has been adopted as the true form of secondary esters of phosphorous acid.

It has been found that the diesters of phosphorous acid may be oxidized, in the presence of a catalyst, to the mono and diesters of phosphoric acid. Monoesters and diesters of phosphoric acid have the formulae:

(HOlnP-O R and . a) p 0 OR Ho-i respectively, wherein R is as defined above.

In accordance with this invention, it has been found that monoand diesters of phosphoric acid and mixtures thereof may be prepared by passing a gas containing "oxygen through a reaction mixture of a diester of phosphorous acid having the formula where R is selected from the group consisting of alkyl, alkenyl, phenyl, alkylphenyl, halo-substituted aryl, haloalkenyl, aralkyl and mixtures thereof, and a catalyst.

The process of this invention may be carried out in the presence of a metal or a metal oxide. Examples of the elements which may be utilized in the practice of this invention are copper, copper oxides and metals selected from the transition elements such as scandium, titanium,

vanadium, chromium, manganese, iron, cobalt, nickel, yttrium, zirconium, niobium, molybdenum, technetium,

ruthenium, rhodium, palladium, rhenium, tungsten, osmium, iridium, platinum, their oxides, and mixtures thereof.

alicyclic,

Suitable dialkyl, halo-substituted dialkyl and dialicyclic phosphites which may be utilized in the present invention may contain from 1 to about 20 carbon atoms in each alkyl, with the more preferred phosphites containing from 1 to about 12 carbon atoms and the most preferred phosphites containing from 1 to about 6 carbon atoms in each alkyl. Preferably, the alicyclic radical has from 4 to 8 carbon atoms. Examples of these phosphites are dimethyl phosphite, diethyl phosphite, dipropyl phosphite, diisopropyl phosphite, dibutyl phosphite, di-tertiary butyl phosphite, dihexyl phosphite, diisohexyl phosphite, diheptyl phosphite, dinonyl phosphite, dicyclohexyl phosphite, didecyl phosphites, didodecyl phosphite, distearyl phosphite, di-2-ch1oroethyl phosphite, di-3-bromopropyl phosphite, di-4-chlorodecyl phosphite, dicyclohexane phosphite, di(3-ethylcyclopentane)phosphite, di(1,3-cyclopentadiene)phosphite, methyl ethyl phosphite, methyl propyl phosphite, methyl hexyl phosphite, 3-brornopropyl methyl phosphite, ethyl butyl phosphite, hexyl decyl phos-.

phite, and the isomers thereof.

Suitable dialkenyl and halosubstituted dialkenyl phosphites which may be utilized in the practice of this invention may contain from 2 to about 10 carbon atoms in each alkylene, with from 2 to about 8 carbon atoms being more preferred and the most preferred phosphites containing from 1 to about 6 carbon atoms. Illustrative of these phosphites are di-(Z-bromo-Z-butene) phosphite, di- (3-chloro-4-heptene) phosphite, di-4-heptene phosphite, diallyl phosphite, dimethallyl phosphite, allyl methallyl phosphite, 2-chloro-2-butene heptene phosphite and di(3 heptene) phosphite, and so forth.

Diaryl, halosubstituted diaryl and diaralkyl phosphites which may be utilized in the practice of this invention are diphenyl phosphite, dibenzyl phosphite, dicresyl phosphite, di(2-decylphenyl) phosphite, di(2-dodecylphenyl) phosphite, di-(2-chlor0phenyl) phosphite, di-(Z-bromophenyl) phosphite, di-(2,6-dichlorophenyl) phosphite, di- (2,4-dibromophenyl) phosphite, di-(Z-iodophenyl) phosphite, phenyl cresyl phosphite, Z-chlorophenyl cresyl phosphite, and so forth. The aryl, halo-substituted aryl, and aralkyl may contain from 6 to about 18 carbon atoms, it being preferred to utilize aryl groups having from 6 to about 10 carbon atoms, with the most preferred embodiment of this invention having the aryl, halo-substituted aryl, and aralkyl containing from 6 to 8 carbon atoms.

In carrying out the process of this invention the phosphite and a suflicient amount of a catalyst are added to a reaction vessel. Oxygen or oxygen contained in a carrier gas, e.g., nitrogen, air, and so forth, is passed through the reaction mixture. A stoichiometric or excess amount of oxygen may be utilized. The excess of oxygen or air utilized may be more than 200 times the stoichiometric amount required to perform the reaction of the invention. Usually, however, one utilizes an excess of oxygen between about 1 and 200 times the stoichiometric amount required, with about 1 to 30 times being preferred and 1 to 15 times being most preferred. When oxygen is in a carrier gas it is preferred to utilize a mixture in the range of about 10-40 percent oxygen and about -60 percent carrier gas.

The amount of catalyst employed in the process of this invention may be between about 0.0001 and 1 mole per mole of secondary phosphite utilized, with between about 0.001 mole and 0.5 mole per mole of phosphite being preferred with between about 0.001 and 0.1 mole of catalyst per mole of phosphite utilized being the most preferred. Usually, a gram weight of from about 0.005 gram and 5 grams of catalyst per molar weight of phosphite may be employed.

The reaction may be carried out at a temperature from about 65 to 300 degrees centigrade, it being more 10 prepared following the above description by passing oxying the invention except as defined in the appended claims. All temperatures are in degrees centigrade and all parts are by weight, unless otherwise set forth.

Examples 16 In these examples a copper oxide catalyst was em ployed. The secondary phosphite, as set forth in Table I, and catalyst were placed in the reaction vessel in the amounts indicated. Oxygen was then passed into the reaction vessel below the level of the mixture for a period of time as indicated in the table.

TABLE I Secondary Phosphites Cupric Oxide Product Analyses Oxygen Catalyst Reaction Reaction 7 v (moles/hour) (parts) time (hours) Temperature Type Moles utilized Percent (R), Percent ROP gen or a gas containing oxygen through a reaction mixture comprising white or yellow phosphorus, a hydroxyl containing compound having the formula wherein R is selected from the group consisting of phenyl, alkylphenyl, halo substituted phenyl, alkyl, halo-substituted alkyl, alkenyl, halo-substituted alkenyl, aralkyl and alicyclic in the presence of a catalyst selected from the group consisting of aluminum, copper, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, rhenium, tungsten, osmium, iridium, platinum, their oxides, and mixtures thereof. The described hydroxyl-containing compound is employed in place of the secondary ester of phosphorous acid. Illustrative of hydroxyl containing compounds which may be utilized are methanol, ethanol, propanol, 2-propanol, butanol, heptanol, decanol, dodecanol, stearyl alcohol, 2-chloropropanol, 3-bromobutanol, propanol, tert-butanol, phenol, cresyl alcohol, dicresyl alcohol, cyclohexanol, 1,3-dimethylA-cyclohexanol, benzyl alcohol, neopentyl alcohol, Z-phenyl-ethanol, and so forth. It is preferred that the alkyl and halo-substituted alkyl contain from 1 to about 20 carbon atoms, with the preferred alkyl and halo-substituted alkyl having 1 to about 12, and the most preferred alkyl and halo-substituted alkyls having from 1 to about 6 carbon atoms. The preferred alkenyl and halo-substituted alkenyl may contain from 2 to about 10 carbon atoms, with the more preferred alkylene and halo-substituted alkylene containing from 2 to about 8 carbon atoms and the most preferred alkenyl and halo-substituted alkenyl containing from 2w 6 carbon atoms. Further, it is preferred that the substituted phenyl, halo-substituted phenyl, and aralkyl contain from 6 to about 18 carbon atoms, with the more preferred substituted phenyl, halo-substituted phenyl, and aralkyl containing from 6 to about 10 carbon atoms, the most preferred substituted phenyl, halo-substituted phenyls and aralkyl containing from 6 to about 8 carbon atoms, and the preferred alicyclic containing 4 to 6 carbon atoms. The hydroxyl containing compound may have a primary, secondary or tertiary hydroxyl. The ratio of alcohol of phosphorus may be from 1:1 to about 10:1 with the preferred ratio being from 1:1 to about 8:1 and the most preferred ratio being from 1:1 to 5:1. It is theorized that the primary and secondary esters of phosphoric acid are formed in this reaction by the oxidation of a secondary ester of phosphorous acid which may be formed as an intermediate for a brief period of time.

The following examples illustrate the process of the invention, however, they are not to be construed as limit- The mixture of the dialkyl phosphate and the monoalkyl phosphate may be separated by known techniques if desired, such as by forming their salts which have different solubilities and then fractionally crystallizing or dissolving, or by chromatographic separation. Analysis of the unseparated residue was carried out with a Sargent Auto Titrater. The products peaked in different areas against a caustic standard to establish the percentage of primary and secondary phosphate present in the product.

Use of scandium, titanium, vanadium, cobalt, yttrium, niobium, technetium, ruthenium, rhodium, rhenium, osmium and iridium, and the oxides of the various metals mentioned earlier will be equivalent to using the metals listed above in this example. Example 6 above (no catalyst) was utilized as a control and establishes that no dialkyl acid phosphate was formed, elements in the first transition series being more preferred.

Instead of the phosphites indicated, di-ter-tiary butyl phosphite, diisohexyl phosphite, distearyl phosphite, dicyclohexyl phosphite, di-3-bromopropy1 phosphite, di-4- chlorodecyl phosphite, ethyl butyl phosphite, hexyl decyl phosphite, di'(2-bromo-2-butene) phosphite, di-4-heptene phosphite, di(2-chlorophenyl)phosphite, dibenzyl phosphite, dicyclohexyl phosphite and dicresyl phosphite, used in the processes of Example 2 results in the corre sponding primary and secondary esters of phosphoric acid.

Example 7 Diethyl phosphite (138 parts) and vanadium pentoxide (0.5 part) were placed in a reaction vessel and heated to about degrees centigrade. Oxygen was passed below the level of the reaction mixture for about 10 hours at 187 milliliters per hour. The initial exothermic reaction was cooled and the temperature was maintained about between degrees and degrees centigrade. Analysis indicated that 56.2 percent of the product was diethyl acid phosphate,

ll r zsOhP OH and 311.9 percent of the product was monoethyl acid phosphate,

Example 8 Example 7 as p a ed util zing d ethyl phosphit (138 parts) and cobalt trioxide (0.5 part). The product analyzed 5.9 percent diethyl phosphate,

and 3-8.7 percent of monethyl phosphate 6. wherein R is as described above, and a catalyst selected from the group consisting of copper, copper oxides, transition elements and their oxides. 1

2. A process in accordance with claim 1 wherein the Example 9 5 catalyst is selected from the group consisting of copper,

Example 7 was repeated utilizing titanium dioxide as a 'icandmm i m i q manganese catalyst. The reaction was run for about 12 hours. Analy- Iron cobalt i ytmum .zlrcomumi mobmm sis showed that 9 percent of the residue recovered was i i technetium pi i rhodlllm panafhum diethyl phosphate 1' emum, tungsten, osmium, llldlum, platinum, thelr ox- 10 ides, and mixtures thereof.

. n 3. A process 1n accordance wlth claim 1 wherein the (O2H50)2P-0H 7 catalyst is copper. I and 5.7 percent of the residue was monoethyl phosphate A P i accordance with claim wherein the catalyst is vanadium pentoxide. H 5. A process in accordance with claim 1 wherein the OiHt0-.-P(0H)i catalyst is cuprous oxide. Examples 1047 6. A process in accordance with claim 1 wherein the catalyst is cobalt trioxide. q ph y y a g c o n 0- 7. A process in accordance with claim 1 wherein the propriate catalyst in the proportions'set forth in Table II catalyst is titanium dioxide were heated with stirring to the desired temperature. 3 A process f the preparation of Secondary esters Oxygen or arr was then added under the surface of the f Phosphoric acid reaction mixture for a period of time as indicated in the aforementioned Table II. The exothermic reaction was 6 maintained within the desired temperature range by H0-P known cooling means. The reaction mixture was titrated at intervals with standard iodine for secondary phosphite. After the phosphite content was less than three percent, as determined by titration with standard iodine, the exwherein R is Selected from the group consisting of y cess hydroxyl containing compound was distilled off. In alkenyl, phenyl, l ph y halo-Substituted p nyl and lieu of cuprous oxide utilized in the examples, it is also alkylphehyl, halo-suhstltuted y halo-Substituted a within the scope of this invention that if elements of the W y 0t 4 t 8 carbon atoms, and P y y first, second and third transition series are employed they comprising Passing Oxygen through a reaction IIliXtllre of will give similar results, elements in the first transition P p a hydroxyl containing compound of the series being the more preferred catalyst to be'employed formula RzOH, wherein R2 is Selected from the group in thi inv ntion, N consisting of phenyl, alkylphenyl, halo-substituted phenyl,

TABLE II Catalyst Conditions Product Ex Hydroxyl Containing Hydroxyl Phosphorus Oxygen Compound Containing (moles) gram moles Parts Time Temp. Diacid Mono acid Compound (per hour) Type (grams) run (hrs) C.) Phosphate Phosphate (moles) (percent) (percent) 1. s 0. 50 0. 50 CuO 0. 1 8.0 113-120 45. 9 a7. 2 1. 5 0. 50 *0. 25 c110 0. a 13. 0 112-120 30. 1 51. 3 1. 5 0. 50 0. 50 Cu 0. 3 5. 0 113-120 45. 5 42. 4 1. 2 0. 40 *0. 25 OuO 0. a 14. 0 95-110 10. 7 24. 2 2. 0 0. 0. 50 CuO 0. 3 12. 0 93-03 51. 0 43. 0 2. 0 0. 50 0. 50 CuO 0. 3 8.0 78-82 40. 0 1s. 0 0. 75 0. 25 0. 25 0110 0. 3 8. 0 97-102 26. 0 2s. 0 Cyclohexyl 1.2 0.40 0.5 Cu 0.3 5.0 115-120 26.0 30.0

*Air was utilized.

While the invention has been set forth in relation to alkyl, halo-substituted alkyl, alkenyl, halo-substituted althe specific examples above, it should be realized that the kenyl, phenylalkyl, and alicyclic of 4 to 6 carbon atoms, invention in its broadest aspects is not so limited. Other and a catalyst selected from the group consisting of copmodifications thereof will become apparent to one skilled per, copper oxides, transition elements and their oxides. in the art upon a reading of this disclosure. Such modifica- 9. A process in accordance with claim 8 wherein the tions are considered to be within the scope of thisincatalyst is selected from the group consisting of alumivention. nurn, copper, scandium, titanium, vanadium, chromium,

What is claimed is: manganese, iron, cobalt, nickel, yttrium, zirconium, nio- 1. A process for the preparation of secondary esters of bium, molybdenum, technetium, ruthenium, rhodium, palphosphoric acid having the formula: ladium, rhenium, tungsten, osmium, iridium, platinum,

0 OR their oxides and mixtures thereof. HO il 10. A process in accordance with claim 8 wherein the catalyst is copper.

OR 11. A process in accordance with claim 8 wherein the wherein R is selected from the group consisting of alkyl, catalyst is CIIPI'OUS oXidth alkenyl, phenyl, alkylphenyl, halo-substituted phenyl and \A Process P P P 'Y and Secondary alkylphenyl, halo-substituted alkyl, halo-substituted alesters of phosphonc and comprising passing oxygen k l, li li of 4 to 3 carbon atoms, d h l lk l through a reaction mixture mainta-inw at a temperature comprising passing oxygen through a reaction mixture of of at least about 65 degrees Centigrade O a Secondary a diester of phosphorous acid of the formula:

ester of phosphorous acid of the formula wherein R is selected from the group consisting of alkyl having from 1 to about 6 carbon atoms, halo-substituted alkyl having from 1 to about 6 carbon atoms, alkenyl having from 2 to about 6 carbon atoms, halo-substituted alkenyl having from 2 to about 6 carbon atoms, phenyl, alkylphenyl, halo-substituted phenyl and alkylphenyl and alicyclic having from 4 to about 8 carbon atoms and from 0.001 to about 0.1 mole per mole of phosphite of a catalyst selected from the group consisting of cuprous oxide, copper, vanadium pentoxide, cobalt trioxide and titanium dioxide and the oxygen being passed through the reaction mixture in an excess equal to from 1 to about 15 times the stoichiometric amount required.

13. A process of preparing primary and secondary esters of phosphoric acid comprising passing oxygen through a reaction mixture, maintained at a temperature of at least about 65 degrees centigrade, of phosphorus and a hydroxyl containing compound having the formula:

wherein R is selected from the group consisting of phenyl, :alkylphenyl phenylalkyl, alkyl, alkenyl, halo-substituted alkyl, halo-substituted alkenyl, and alicyclic having from 4 to about 6 carbon atoms, and from 0.001 to about 0.1 mole per mole of phosphorus of a catalyst selected from the group consisting of copper and cuprous oxide, the alcohol and phosphorus present in a ratio of from 1:1 to :1.

14. A process of preparing a primary ester of phosphoric acid comprising passing oxygen through a reaction mixture maintained at a temperature of at least about 65 degrees centigrade of a secondary ester of phosphorous acid of the formula wherein R is selected from the group consisting of alkyl having from 1 to about 6 carbon atoms, halo-substituted alkyl having from 1 to about 6 carbon atoms, alkenyl having from 2 to about 6 carbon atoms, halo-substituted alkenyl having from 2 to about 6 carbon atoms, phenyl alkylphenyl, halo-substituted phenyl and alkylphenyl and alicyclic having from 4 to about 8 carbon atoms and from 0.001 to about 0.1 mole per mole of phosphite of a catalyst selected from the group consisting of cuprous oxide, copper, vanadium pentoxide, cobalt trioxide and titanium dioxide and the oxygen being passed through the reaction mixture in an excess equal to from 1 to aboutlS times the stoichiometric amount required.

. 15. A process of preparing a primary ester of phosphoric acid comprising passing oxygen through a reacti-on mixture, maintained at a temperature of at least about degrees Centigrade, of phosphorus and a hydroxyl containing compound having the formula:

R OH

wherein R is selected from the group consisting of phenyl, alkylphenyl phenylalkyl, alkyl, alkenyl, halo-substituted alkyl, halo-substituted alkenyl, having from 2 to 6 carbon atoms, and alicyclic having from 4 to about 6 carbon atoms, and from 0.001 to about 0.1 mole per mole of phosphorus of a catalyst selected from the group con sisting of copper and cuprous oxide, the alcohol and phosphorus present in a ratio of from 1:1 to 5:1.

References Cited UNITED STATES PATENTS 2,921,087 1/ 1960 Coover et a1. 260-985 X 2,952,699 9/1960 Norman 260-985 3,136,805 6/1964 Baranauck as et a]. 260-985 3,167,577 1/ 1965 Malone 260-971 CHARLES B. PARKER, Primary Examiner. F. M. SIKORA, A. H. SUTTO, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,333,030 July 25, 1967 Charles F. Baranauckas et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 4 lines 6 5 to 6 8, the formual should appear as shown below instead of as in the patent:

i C H 0i(OH) column 8, line 4, for "phenyl" read phenyl,

Signed and sealed this 22nd day of April 1969. (SEAL) Attest:

Edward M. Fletcher, J r. EDWARD J BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE PREPARATION OF SECONDARY ESTERS OF PHOSPHORIC ACID HAVING THE FORMULA:
 8. A PROCESS FOR THE PREPARATION OF SECONDARY ESTERS OF PHOSPHORIC ACID 